Reliability handling for wireless transceivers

ABSTRACT

Techniques maintaining receiver reliability, including determining a present attenuation level for an attenuator, wherein the attenuation level is set by a gain controller, determining a relative reliability threshold based on the present attenuation level, receiving a radio frequency (RF) signal, determining a voltage level of the received RF signal, comparing the voltage level of the received RF signal to the relative reliability threshold to determine that a reliability condition exists, and overriding, in response to the determination that the reliability condition exists, the present attenuation level set by the gain controller with an override attenuation level based on the present attenuation level.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.17/112,137, filed Dec. 4, 2020, which claims priority to IndiaProvisional Application No. 201941050156, filed Dec. 5, 2019, entitled,“RX/FB Relative Reliability Handling in Wireless Transceivers”, whichare hereby incorporated by reference.

BACKGROUND

Wireless systems usually include wireless transceivers used to transmitand receive wireless signals. Often these transceivers need to be ableto support a relatively wide dynamic range of received signal power, forexample with a power level of −60 dBm to 20 dBm. To help support widedynamic ranges, these transceivers often include low noise amplifiers(LNAs) which provide amplification to the received signals. Generally,gain refers to a ratio between output voltage and input voltage. TheseLNAs often include a gain setting that may be adjusted by an automaticgain controller (AGC), which can be used to help prevent damagingcomponents of the transceivers, such as a digital step attenuator (DSA),by reducing the gain when a relatively high-voltage signal is received.For example, to receive a high voltage signal, the gain of an LNA and/oran adjustable gain of the DSA may be adjusted by the AGC. However,certain relatively high-voltage signals may be a concern. When arelatively high gain setting is used to help receive a relatively lowvoltage signal and a relatively high-voltage signal, such as from a veryclose transmitter, is received, the AGC may not be able to adjust theDSA gain quickly enough and the DSA may be damaged. Additionally, highvoltage levels over some relatively long periods of time can causetransceivers to be saturated, resulting in potential reliability issues.

SUMMARY

This disclosure relates to a technique related to maintaining receiverreliability, including determining a present attenuation level for anattenuator, wherein the attenuation level is set by a gain controller.The technique further includes determining a relative reliabilitythreshold based on the present attenuation level, receiving a radiofrequency (RF) signal, and determining a voltage level of the receivedRF signal. The technique further includes comparing the voltage level ofthe received RF signal to the relative reliability threshold todetermine that a reliability condition exists. The technique furtherincludes overriding, in response to the determination that thereliability condition exists, the present attenuation level set by thegain controller with an override attenuation level based on the presentattenuation level.

Another aspect of the present disclosure relates to a receivercomprising a gain controller configured to set a present attenuationlevel for an attenuator. The receiver may also include a reliabilitydetector module configured to determine a relative reliability thresholdbased on the present attenuation level. The receiver may also include adetector configured to receive a radio frequency (RF) signal, anddetermine a voltage level of the received RF signal. The receiver mayalso include an override value module configured to: compare the voltagelevel of the received RF signal to the relative reliability threshold todetermine that a reliability condition exists, and override, in responseto the determination that the reliability condition exists, the presentattenuation level set by the gain controller with an overrideattenuation level based on the present attenuation level.

Another aspect of the present disclosure relates to an electronic devicecomprising one or more processors, a memory, and a reliability detectormodule configured to determine a relative reliability threshold based ona present attenuation level. The electronic device may also include adetector configured to: receive a radio frequency (RF) signal anddetermine a voltage level of the received RF signal. The electronicdevice may also include an override value module configured to: comparethe voltage level of the received RF signal to the relative reliabilitythreshold to determine that a reliability condition exists and override,in response to the determination that the reliability condition exists,the present attenuation level set by the gain controller with anoverride attenuation level based on the present attenuation level.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various examples, reference will now bemade to the accompanying drawings in which:

FIG. 1 illustrates an example circuit for absolute reliability handlingin wireless receivers.

FIGS. 2A and 2B illustrates an example circuits for relative reliabilityhandling, in accordance with aspects of the present disclosure.

FIG. 3 is a flowchart for reliability handling, in accordance withaspects of the present disclosure.

FIG. 4 is a flow diagram illustrating a technique for receiverreliability handling, in accordance with aspects of the presentdisclosure.

DETAILED DESCRIPTION

Wireless receivers, such as those used for wireless base stations,evolved Node B's, access points, mobile devices, etc., often need tosupport a wide dynamic range of received, or input, signal voltagelevels. Components of the receivers, such as a DSA, are quite sensitiveand can be degraded by too high an input voltage level. To help preventthis, and also to enhance the supported dynamic range, receivers mayinclude components with an adjustable gain that may be controlled by anadjustable gain controller (AGC). It may be understood that transceiversinclude components for receiving and sending wireless signals and as theconcepts discussed herein with respect to receivers apply totransceivers as well. The AGC may assert a signal to the LNA and/or theDSA to reduce the gain, or even attenuate, the voltage of the inputsignal based on the input voltage level to reduce the voltage of anoutput of the DSA, which is then passed on to a radio frequency analogto digital converter (RF-ADC). Attenuation generally refers to a gainsetting of less than 1, which thereby results in a voltage level of theoutput signal that is smaller than the voltage level of the inputsignal.

As an example, FIG. 1 illustrates an example circuit 100 for absolutereliability handling in wireless receivers. In some cases, absolutereliability may refer to a condition where a received signal voltagelevel of an input signal is above a threshold maximum voltage level. Forexample, if a device, such as a DSA, may be damaged, and become lesssensitive to input, by signal voltages above a certain voltage levelover a period of time and it is desirable to minimize the cumulativeamount of time the device is exposed to those signal voltages above acertain voltage level. The circuit 100 illustrates an RF samplingreceiver including an LNA 114, peak detector 102, window counter 110,DSA 104, RF-ADC 106, decimation filter chain 108 and AGC 112. The LNA114 is coupled to a peak detector 102 and DSA 104. The peak detector 102is in turn coupled to a window counter 110 and the DSA 104. The DSA iscoupled to a RF-ADC 106. The RF-ADC 106 is coupled to an AGC 112. TheAGC 112 is coupled to the DSA 104 and LNA 114. It may be understood thatwhile FIG. 1 illustrates an RF sampling receiver, the techniquesdiscussed herein are also applicable to other RF receiver designs, suchas direct conversion (e.g., zero intermediate frequency) receivers. Thecircuit 100 includes a peak detector 102, but other types of detectorscan be used, such as a root mean square power detector. The peakdetector 102 is configured to detect the peak voltage level of an inputsignal 116. In this example, the peak detector 102 is also configured todetect an absolute reliability condition where a received signal voltagelevel of the input signal 116 is above a threshold maximum voltagelevel.

In some cases, a level of attenuation of an LNA 114 and/or the DSA 104may be controlled, for example, by an AGC 112 which may be downstream ofa RF-ADC 106 and a decimation filter chain 108. In some cases, the DSA104 may include multiple gain modes, such as a high-gain mode or alow-gain mode, and each gain mode may provide varying amounts of gainadjustability. For example, different gain modes may have differentranges of gain settings and some gain modes may have a wider range ofsupported gain settings than other gain modes. The AGC 112 may beinternal to the receiver circuit, or external to the receiver circuit.Similarly, the LNA 114 may be internal or external to the receivercircuit. Adjusting the gain of the DSA 104 with the downstream AGC 112may not be sufficient to prevent reliability issues of the DSA due to anamount of time that may be needed for the AGC to detect and respond tothe absolute reliability condition. Thus, overriding the gain setting ofthe AGC may be desired. For example, where an input signal 116 isreceived with a received signal voltage level above a predeterminedabsolute threshold maximum level, such as voltage corresponding to 12dBm, the peak detector 102 may determine that an absolute reliabilitycondition exists and override the present attenuation level of a DSA 104set, for example, by the AGC. When overriding the present DSA setting,the peak detector 102 may, for example, set the DSA 104 attenuationlevel to a maximum attenuation level or some other predeterminedattenuation level based on the received signal voltage level.

In some cases, a signal with a voltage level below the predeterminedabsolute threshold maximum voltage level but sustained for a substantialperiod of time may also saturate the DSA and cause relative reliabilityissues. As an example, a DSA, at a certain setting may be damaged by aninput signal voltage that is lower than the voltage of the absolutereliability threshold, if that input signal voltage is sustained oversome period of time. While a signal voltage may be below the absolutereliability threshold, the signal voltage may be higher than asaturation level of the DSA at some gain settings of the DSA. Forexample, for some gain settings of the DSA there is a voltage level suchthat an input signal beyond the voltage level will saturate the DSA. Ifthe input signal voltage is higher than this voltage level is sustainedfor a period of time, the DSA may be damaged. To help address suchissues, a peak detector 102 may be used to detect voltage peaks withinan RF frame that may cause reliability issues. For example, the peakdetector 102 may sample input level at a particular frequency and ateach sample instance, the peak detector 102 may output an indication(e.g., a logic high (1) if the sampled voltage is above a thresholdvoltage level configured for the peak detector 102 and a logic low (0)if the sampled voltage is below the threshold voltage level configuredfor the peak detector 102) whether the sampled voltage is above athreshold voltage level. In certain cases, the peak detector 102 voltagelevel threshold level maybe configured based on, for example, the DSAattenuation level.

Window counter 110 is incremented responsive to each instance of a 1from the peak detector 102. If the window counter 110 exceeds apredetermined hit threshold a reliability condition may be asserted. Inresponse to detection of the reliability condition (i.e., windowcounter's count value exceeding the predetermined hit threshold), thewindow counter 110 asserts a signal 118 to the DSA 104 to cause theattenuation setting for the DSA 104 to be overridden to a newattenuation setting. In some cases, the threshold voltage level of thepeak detector 102 and/or the hit threshold of the window counter may beconfigurable. For example, the hit threshold of the window counter maybe a programmable value in a register that can be set by an externalmaster, such as a micro-controller, serial peripheral interface, etc.The value of the hit threshold may be determined, for example, based oncircuit design, testing, manufacturing, etc. As another example, the hitthreshold of the window counter may be a predetermined value set as apart of circuit design, testing, manufacturing, etc.

In some cases, after one or more RF frames are received with a voltagelevel below the threshold voltage level, the window counter 110reliability condition may be reset. After a reliability condition isdetected, a different voltage level threshold and window counter 110 maybe set. For example, the voltage level threshold may be reduced once theinitial voltage level threshold is hit. In some cases, the windowcounter 110 may count to a release length number and accumulate a numberof sample instances received with a voltage level above the thresholdvoltage level. After the release length number is reached, theaccumulated number is compared to a release threshold number. If therelease condition window counter is below the release threshold number,then the reliability condition may be released (e.g., reset).

As transistor sizes shrink, the voltage rating of transistors is alsoreduced. This reduced voltage capacity can raise issues with relativereliability, in addition to the absolute reliability issues discussedabove. Relative reliability is related to the voltage of a receivedsignal as compared to a full scale (FS) signal. For digital systems,there is a defined maximum digital signal peak amplitude, or voltage,level, defined as 0 dBFS. This full-scale signal can vary based on alevel of DSA attenuation being applied. Generally, a signal above 0 dBFSwill saturate a receiver, but a signal above 0 dBFS but below apredetermined absolute reliability threshold may not raise a reliabilityissue. In some cases, voltage levels for a received signal above afull-scale voltage level, but below the predetermined absolutereliability threshold, may cause relative reliability issues. Forexample, for a DSA setting of 0 dB, a full-scale signal may be −1 dBm.If, however, an 8 dBm signal is received, this signal is +9 dB higherthan the full-scale signal or 0 dBFS voltage level supported by the DSAsetting. This 8 dBm input signal is +9 dB signal relative to thefull-scale signal 0 dBFS for the given DSA setting. This signal voltagelevel, while still below, for example, a 12 dBm predetermined absolutethreshold maximum voltage level, may still cause reliability issues forthe receiver. In accordance with aspects of the present disclosure, areliability threshold may be determined based on a DSA attenuationsetting in addition to, or instead of, the predetermined absolutethreshold maximum voltage level.

FIG. 2A illustrates an example circuit 200 for relative reliabilityhandling, in accordance with aspects of the present disclosure. Circuit200 includes an input signal 201 input to a DSA 204 and an RF peakdetector 202A. An output of the DSA 204 is coupled to an input of RF-ADC206. An output of the RF-ADC 206 is coupled to an input of a decimationfilter chain 208 and input of digital peak detectors 224. An output ofthe decimation filter chain 208 is coupled to an input of gaincompensation module 218, which, in turn, outputs to an AGC 212 andanother circuit. An output of the digital peak detectors 224 is coupledto an input of a gain compensation module 220. An output of the gaincompensation module 220 is coupled to an input of the AGC 212. An outputof AGC 212 is coupled to an input of an override value module 214 of again controller module 222. Another output of AGC 212 is coupled to aninput of a reliability detector 210. An output of the override valuemodule 214 is coupled to an input of a gain compensation value module216 of the gain controller module 222. An output of the gaincompensation value module 216 is coupled to an input of the gaincompensation module 218 and an input of the gain compensation module220. An output of the override value module 214 is also coupled to aninput of the DSA 204. The RF peak detector 202A is communicativelycoupled to reliability detector 210 and an output of the RF peakdetector 202A may be coupled to an input of the reliability detector210. An output of the reliability detector 210 may pass peak detectorthresholds to an input of the RF peak detector 202A. An output ofreliability detector 210 is coupled to an input of override value module214 and the reliability detector 210 may output a reliability indicatorand a DSA setting to the override value module 214. In certain cases,the reliability indicator may be set to high to indicate that the DSAsetting from the reliability detector 210 should be used to override theDSA setting from the AGC 212.

As shown, circuit 200 includes an RF peak detector 202A for detectingthe peak signal voltage level of the input signal 201, a DSA 204, a RFADC 206, and a decimation filter chain 208. The DSA 204 is configured toprovide an adjustable amount of attenuation for the input signal 201based on a reliability detector 210 and an AGC 212 in conjunction withthe gain controller module 222. The gain controller module 222 mayreceive gain information from the AGC 212 as well as information fromthe reliability detector 210 to determine whether the gain should beoverridden. In this example, the gain controller module 222 includes anoverride value module 214 for determining a gain override value and again compensation value module 216 to determine a gain compensationvalue. In some cases, the AGC 212 may be integrated along with othercomponents of circuit 200. In some cases, the AGC 212 may be coupled to,but external to components of circuit 200, such as a part of a separateapplication specific integrated circuit (ASIC). In non-overrideoperation, an attenuation setting of the DSA 204 is directly controlledby the AGC 212. While the attenuation setting may be in any form orunit, for clarity DSA settings are discussed in terms of decibels, wheredecibels are 20×log 10(gain), where gain is in a linear scale. Gain maybe equal to the output/input voltage in milliwatts. In this exampleembodiment, the AGC 212 receives a digital signal, as converted from ananalog signal to a digital signal by the RF-ADC 206. The AGC 212determines a DSA setting for the DSA 204. For example, in a case where arelatively low voltage input signal is received, the AGC 212 maydetermine a threshold voltage which may saturate the DSA 204 anddetermine that the relatively low voltage signal is far from saturatingthe DSA 204. Based on the saturation measurement, the AGC 212 maydetermine an attenuation setting for the DSA 204. For example, the AGC212 may utilize a lookup table, adjusting attenuation settings when thereceived signal is detected above the threshold voltage and continuingto adjust the attenuation signals if additional received signals arestill above the threshold voltage. In certain cases, the AGC mayincrease the gain until the resulting voltage crosses a first targetthreshold voltage and reduce the gain until the resulting voltagecrosses above a second target threshold voltage. In this manner, the AGCmay increase and/or decrease the DSA attenuation setting (e.g., DSAgain) to maintain the signal voltage between the first and second targetthresholds, helping to maximize a signal to noise ratio. In thisexample, the AGC 212 may determine that the attenuation setting may bereduced to effectively increase the gain applied to the input signal201. The AGC 212 sends the DSA setting information to the DSA 204 viathe gain controller module 222 and the reliability detector 210 obtainsthe DSA setting information. In some cases, the DSA setting informationmay include a value from the AGC adjusting the DSA gain.

In some cases, the AGC 212 may determine the DSA setting based on theinput signal 201 signal. However, if a reliability condition, eitherabsolute or relative, is detected, the reliability detector 210 maydetermine a different DSA setting. FIG. 2B illustrates an examplecircuit for a reliability detector 210, in accordance with aspects ofthe present disclosure. The reliability detector 210 may include areliability state machine 252 for detecting and responding toreliability conditions. The reliability state machine may be coupled toan output of the AGC (not shown) and receive DSA setting informationinput from the AGC. The reliability state machine 252 may also becoupled to and output to a window counter controller 254. The windowcounter controller 254 may be communicatively coupled to a windowcounter 256, which may output to an accumulator 258. The accumulator 258may also accept input from the RF peak detector 202A and output to athreshold comparator 260. The threshold comparator 260 may becommunicatively coupled to the reliability state machine 252. Thereliability state machine 252 may output to the gain override module214.

The reliability state machine 252 may output to the window countercontroller 254, a signal indicating a window length 262 (e.g., period oftime of the window). This window length 262 may indicate a period oftime to wait before resetting a window counter if an input signal beyondthe threshold voltage level is not received within the period of time.This window length 262 may be adjusted, for example, if an input signalbeyond the threshold voltage is received. The window counter controller254 may receive a counter state indication 264 from the window counter256 indicating whether the window counter 256 is running to track areliability condition. The window counter controller 254 may also asserta window reset signal 266 to the window counter 256 when the period oftime has passed. The window counter 256 may assert an accumulator resetsignal 268 to the accumulator 258 when the window counter is beingreset. The RF peak detector 202A may regularly determine the inputsignal voltage level and output 270, for example, a value, such as 1,indicating whether the input signal voltage level is above a peakdetector threshold or another value, such as 0, indicating that theinput signal voltage is below the peak detector threshold. Theaccumulator 258 counts a number of times the input signal voltage levelis above the peak detector threshold and outputs this number to thethreshold comparator 260. The reliability state machine 252 may alsooutput to the RF peak detector 202A and set the peak detector thresholds272. The threshold comparator 260 determines whether the reliabilitycondition is still present by monitoring the output of the accumulator258 for changes to the number of times the input signal voltage level isabove the peak detector threshold within a number of hits threshold 274received from the reliability state machine 252. The thresholdcomparator 260 may output 276 to the reliability state machine 252indicating whether the reliability condition is present. Based on output276, the reliability state machine 252 may determine if the reliabilitycondition is present or not.

Returning to FIG. 2A, based on the DSA setting information, thereliability detector 210 determines a relative reliability threshold. Insome cases, the relative reliability thresholds may differ for some oreach of the DSA settings. As an example, the relative reliabilitythreshold may be configured to be 9 dB higher than the voltage level of0 dBFS of the present DSA gain. Thus, as a more specific example, wherethe present DSA setting is 0 dB the 0 dBFS voltage level, which, in thisexample, corresponds to −1 dBm, the relative reliability threshold, ifconfigured to be 9 dB higher than the voltage level of 0 dBFS, at thepresent DSA setting of 0 dB would correspond to 8 dBm. In some cases,the relative reliability thresholds for the DSA settings may beconfigurable or programmable, or based on a particular hardwareconfiguration, such as the external AGC type, RF-ADC type, DSA type, orbands being received. For example, a set of registers or a lookup tablemay be provided to store the relative reliability thresholds and theseregisters may be externally accessible to allow the relativelyreliability thresholds to be adjusted. The relative reliabilitythresholds may be, in some cases, predetermined and stored in a memory.

Once a relative reliability threshold is determined for a present DSAsetting, a voltage level for a received signal, as determined by thepeak detector 202A, is compared to the relative reliability threshold.In some cases, the peak detector 202A may be configured to regularlydetermine the input signal voltage level, such as 128 or 256 times persecond, and output this signal voltage level information to thereliability detector 210. For example, the peak detector can regularlyoutput a binary signal with a value indicating whether the input signalvoltage level is above or below the relative reliability threshold. Thereliability detector 210 may receive the signal voltage levelinformation and count a number of instances in which the signal voltagelevel exceeds the relative reliability threshold for a given timeperiod. If the number of instances exceeds a number of peaks (e.g.,number of instances where the signal voltage level exceeds therelatively reliability threshold) threshold, the reliability detector210 may determine that the received signal has exceeded the relativereliability threshold and that a relative reliability condition exists.In some cases, the number of peaks threshold may be configurable, forexample by a user. For example, one or more registers may be provided tostore the number of peaks threshold and these registers may beexternally accessible to allow the a number of peaks thresholds to beadjusted.

Returning to the earlier example where the relatively low voltage signalis being received, another transmitter may start to transmit arelatively high-voltage signal to the receiver. This relativelyhigh-voltage signal may be received and the voltage level for thereceived signal may be determined to exceed the relative reliabilitythreshold based on, for example, twenty instances over a course of 128measurements of the peak detector to be 9 dB, higher than the 0 dBFSvoltage level, at the present DSA setting of 0 dB, of −1 dBm.

If the voltage of a received signal exceeds the relative reliabilitythreshold, an override value module 214 may determine a gain overridevalue. In some cases, this gain override value may be based on thepresent DSA setting and/or as an offset value from the present DSAsetting. In some cases, the gain override value may be based on therelative reliability threshold. For example, the gain override value maybe determined based on a difference between the relative reliabilitythreshold for the present DSA setting and the voltage level for thereceived signal. Returning to the previous example, as the receivedsignal has a voltage level of 9 dBm and the relative reliabilitythreshold is 8 dBm, the gain override value may be determined to be 1dB. In other cases, the gain override value may be configurable. As asecond example, if an incoming signal voltage level is 9 dBm and therelative reliability threshold is 8 dBm for a 0 dB DSA setting, theoverride gain value may be determined to be 9 dB. Once the gain overridevalue is determined, the present DSA setting is overridden based on thegain override value. Returning to the previous example, the present DSAsetting of 0 dB may then be overridden and set to an overridden DSAsetting of 1 dB. In the second example, the present DSA setting of 0 dBmay be overridden and set to the overridden DSA setting of 9 dB.

Overriding the AGC 212 settings for the DSA 204 could, in some cases,result in undesirable feedback loops. For example, if the present DSAsetting is overridden to increase the DSA settings, attenuation isincreased, which effectively reduces the gain of received input signalsand saturation of the DSA 204. If the AGC 212 detects that saturationhas decreased, the AGC 212 may attempt to lower the DSA setting, therebyincreasing the amplitude of the signal provided to the RF-DAC 206. Gaincompensation may be used to help address such potential feedback loops.A gain compensation value module 216 determines a gain compensationvalue. In some cases, the gain compensation value may be based on thegain override value determined by the override value module 214. Thegain compensation value module 216 may, in some cases, be combined withthe override value module 214. In some cases, the AGC 212 may be coupleddownstream of the decimation filter chain 208. In such cases, a gaincompensation module 218, coupled between the decimation filter chain 208and the AGC 212, may apply gain compensation to a digital signal inputto the gain compensation module 218, effectively increasing a gain of anoutput digital signal 226. In some cases, the AGC 212 may be coupled 228upstream of the decimation filter chain 208 to directly sample a digitalversion of the received analog signal. In some cases, the gaincompensation module 220 may be configured to support a higher bandwidth,such as 2-3 GHz, as compared to gain compensation module 218 as the gaincompensation module 220 is sampling data prior to the decimation filterchain 208.

In some cases, the AGC 212 may receive the gain compensated output ofthe gain compensation modules 218, 220 and use the output to help theAGC 212 to effectively see that the RF-ADC 206 is saturating. The AGC212 may then help adjust the DSA setting appropriately, such as byincreasing the DSA attenuation setting. In some cases, the AGC 212 maybe an external AGC. As an example of an external AGC, the AGC may beintegrated as a part of a separate circuit or chip from the RF-ADC 206,DSA 204, and decimation filter chain 208. The external AGC, in suchcases, is communicatively coupled to the gain controller module 222.

FIG. 3 is a flow chart 300 for reliability handling, in accordance withaspects of the present disclosure. In this example embodiment, the flowchart 300 illustrates a technique for detecting absolute and relativereliability conditions. In some cases, the reliability state machine 252of FIG. 2B may implement the techniques shown in flow chart 300. Where areceiver is configured to detect both absolute and relative reliabilityconditions, the reliability condition being checked may be determined,in some cases, by the DSA setting. For a particular DSA setting, atblock 302, a relative reliability threshold is determined, for exampleby reliability detector 210 as discussed above. In some cases, thisthreshold may be used to determine settings for the analog RF peakdetector. At decision block 304, a determination is made, for example byreliability detector 210, as to which threshold voltage level to use.Which threshold voltage level to use can be expressed as a functionmin(voltage level at 0 dBFS (or present DSA setting)+relativereliability threshold, absolute reliability threshold). Thus, thefunction finds the minimum of either a voltage level at 0 dBFS plus therelative reliability threshold or the absolute reliability. Thisexpression may be evaluated by the peak detector 202A, or the statemachine 252 of FIG. 2B, to detect a relative reliability condition belowa particular DSA attenuation setting. Above the particular DSAattenuation setting, detecting an absolute reliability condition isgiven a higher preference. As an example, assume for a particularreceiver if the 0 dBFS voltage level with 0 dB DSA setting is 0 dBm andan absolute reliability attenuation level setting at 20 dBm. For the 12dB DSA, the 0 dBFS voltage level would be 0+12=12 dBm. If the relativereliability threshold is 9 dB, the relative reliability voltage levelwould be 12+9=21 dBm. However, if, as in this example, there is anabsolute reliability voltage threshold at 20 dBm, the 12 dB DSA gainsetting would exceed the absolute reliability voltage threshold. In somecases, the determination of block 304 may be included in state 302.Thus, a determination may be made that at a DSA attenuation setting of11 dB or higher, the input voltage level may be checked for the absolutereliability condition, for example, by a peak detector, at block 306 andbelow the DSA attenuation setting of 11 dBm, the input voltage level maybe checked for the relative reliability condition at state 320, forexample, by another peak detector.

As a more specific example where the input voltage level is checked forrelative reliability, assume that the particular receiver embodimentdiscussed in the previous example with a DSA attenuation setting of 0dBFS receives an input signal with a voltage level of 10 dBm. As thisinput signal voltage is above the relative reliability threshold of 9dBm, the relative reliability condition is detected at decision block320 in a manner as discussed above with respect to the reliabilitydetector 210. In this example, at block 322, the DSA setting isoverridden based on the determined gain override value offsetcorresponding to a DSA setting of 9 dB. In some cases, an override stateindicator, such as a flag, register entry, or bit, is set indicatingthat the DSA setting has been overridden. At block 324, a correspondinggain compensation value may be determined based on the DSA overridesetting, for example as an offset value. As there was a change in theDSA settings, control returns, via decision block 334, to block 302. Asthe 9 dB DSA setting is still below 11 dB, input voltage continues to bechecked for relative reliability condition at decision block 320 with asecond relative reliability threshold. As the DSA settings were changedin a first round of overriding the DSA setting, the relative reliabilitythreshold (e.g., the second relative reliability threshold) isdetermined again at block 302. Assuming the second relative reliabilitythreshold is also 9 dB above 0 dBFS at a 9 dB DSA attenuation setting,the second relative reliability threshold is determined to be 18 dBm.Assuming the received signal voltage continues to be measured at 10 dBm,the received voltage is less than the 18 dBm second relative reliabilitythreshold, and a second relative reliability condition is not present.

In another relative reliability example, assume an input signal voltagemeasured at 21 dBm is received with the particular receiver embodimentdiscussed in the previous example again with a DSA attenuation settingat 0 dB. Similar to the first round of overriding the DSA settingdescribed above, as the 21 dBm input signal voltage is above therelative reliability threshold, the relative reliability condition isdetected at decision block 320. At block 322, the DSA is overriddenbased on the determined gain override value corresponding to a DSAsetting of 9 dB and an override state indicator may be set. Acorresponding gain compensation value may be determined based on the DSAoverride setting at block 324. As the 9 dB DSA setting is still below 11dB, input voltage continues to be checked for relative reliabilitycondition at decision block 320 with a second relative reliabilitythreshold set to 18 dBm, as discussed above.

Assuming the input signal voltage continues to be measured at 21 dBm, asecond relative reliability condition is detected at decision block 320and the DSA setting is again overridden by an offset of 9 dB, the DSAsetting is then set to 18 dB. As there was a change in the DSA settings,control returns, via decision block 334, to block 302. A third relativereliability threshold is calculated at 18 dBm+9 dB=27 dBm. At decisionblock 304, a new peak detector threshold is determined where min(18dBm+9 dB, 20 dBm)−18 dBm=2 dB higher than the 0 dBFS voltage level at 18dB DSA attenuation. As the DSA setting is 18 dB, which is higher thanthe 11 dB DSA setting, the input signal is checked for absolutereliability and a determination whether an absolute reliabilitycondition exists is made at block 306 by comparing the input signalvoltage level to the absolute reliability attenuation level threshold.Where the input signal voltage continues to be 21 dBm, an absolutereliability condition exists and at block 308, a determination is madeto override the DSA setting. At state 310, the DSA setting isoverridden, for example, by a maximum level setting of the DSA, oranother DSA level setting based on predetermined level. In some cases, again compensation value may be applied, or the output of the decimationfilter chain may be saturated. After the reliability condition is nolonger appropriate, it may be desirable to release the DSA override.

Flowchart 300 also illustrates example techniques for releasing the DSAoverride. In this example, a determination to release the DSA overrideapplied in response to an absolute reliability condition may be made atdecision block 312. As an example, the determination that the DSAoverride should be released may be based on a determination that theinput voltage level has dropped below the absolute reliabilityattenuation level threshold or after a some period of time has passed.In some cases, this period of time may correspond to a window length forresetting a window counter. This period of time may be indicated to thewindow counter. If the input voltage level has dropped, then the DSAoverride may be removed at block 314. If gain compensation waspreviously applied, or if the output of the decimation filter chain wassaturated, these may also be removed at block 314.

For a relative reliability condition, there may be multiple techniquesfor releasing the DSA override. A first technique may be based onobservations of the response of the AGC. Returning to the examplediscussed above with the input signal voltage measured at 10 dBm, afterthe DSA setting is overridden corresponding to a DSA setting of 9 dB, atblock 324, a corresponding gain compensation value is determined atstate 326. This gain compensation value may be used to increase the gainof a digital signal received by the AGC. In some cases, the AGC maydetect an increase in the saturation of the digital signal received andincrease the attenuation setting of the DSA. Returning to the example,after the gain compensation value is determined, control returns, viablocks 334, 302, and 304, to decision block 320 where input signalvoltage is checked for a second relative reliability condition atdecision block 320. As the second relative reliability threshold isdetermined to be 18 dBm, the input signal voltage is not sufficient totrigger a second relative reliability condition. At decision block 326,the override state indicator, set at block 322, may be checked. As theoverride state indicator is set, a difference between the DSA overridesetting and an updated DSA setting requested by the AGC is determined atblock 328. An updated gain compensation value may also be determinedbased on the updated DSA setting and the DSA override setting. Atdecision block 330, the difference between the DSA override setting andan updated DSA setting requested by the AGC is checked to see if it isless than a decay threshold. In some cases, this decay threshold may beconfigurable and may include a check to ensure that the AGC has updatedthe DSA setting to increase attenuation. That the AGC has updated theDSA setting to increase attenuation and that the difference between theupdated DSA setting and the DSA override setting is below the decaythreshold indicates that the AGC has noticed and responded to addressthe relative reliability condition. At block 332, the DSA override maybe removed (e.g., released), along with any digital gain compensationapplied, and the override state indicator cleared. If the AGC has notupdated the DSA and/or if the difference is above the decay threshold,then the DSA override is maintained at block 336. If necessary, theupdated gain compensation value may be used to adjust the digital gaincompensation.

Another technique for releasing the DSA override for a relativereliability condition may be time based. For example, a transienthigh-voltage input signal may trigger a relative reliability conditionresulting in a DSA override. This signal may be just long enough totrigger the DSA override but not long enough to be detected by the AGC.Thus, there may be a configurable maximum time duration for the relativereliability condition, after which the DSA override may be removed. Thismaximum time duration may be configured to be relatively long andsufficient for the AGC to have multiple opportunities to detect andreact. A check to ensure that a DSA override time duration is less thanthe maximum time duration (e.g., decay threshold) may be performed atblock 330, for example by a reliability detector. If the DSA overridetime duration is greater than the maximum time duration, then the DSAoverride is released and the DSA override time duration is reset. Ifanother high-voltage input signal is received, another DSA override maybe imposed.

In some cases, a receiver may include more than a single peak detector.For example, circuit 200 in FIG. 2A may include multiple RF peakdetectors 202A and 202B. Where multiple peak detectors are available,one of the peak detectors may be configured to detect an absolutereliability condition and another peak detector may be used to detect arelative reliability condition. In such cases, the determination whethera reliability condition and/or absolute reliability condition exists maybe performed in a manner similar to that described above. Releasing theDSA override with multiple peak detectors may be similar to thatdescribed above for embodiments with a single peak detector. In somecases, with multiple peak detectors, a first peak detector may beconfigured to detect both absolute and relative reliability conditionsand a second peak detector may be configured to detect an input voltagelevel based on the threshold for the peak detector. In such cases, whenan override condition is present, the second peak detector may be usedto determine whether the input voltage level has fallen below thethreshold and thus the override condition is no longer present andrelease the DSA override.

FIG. 4 is a flow diagram 400 illustrating a technique for receiverreliability handling, in accordance with aspects of the presentdisclosure. At block 402, a present attenuation level for an attenuatoris determined. The attenuator level indicates an amount of attenuationto be applied to a received RF signal and may be determined by the AGCin conjunction with a gain controller, such as gain controller module222, and a reliability detector, such as reliability detector 210. Atblock 404, a reliability threshold is determined based on the presentattenuation level. For example, a relative reliability threshold may bedetermined, for example by a reliability detector, such as reliabilitydetector 210, based on the present attenuation level set by the gaincontroller. In some cases, this relative reliability threshold may bebased on an offset from the attenuation level and a full-scale signal.At block 406, a radio frequency (RF) signal is received. For example,one or more peak detectors, such as peak detector 202A and/or peakdetector 2026, may receive an analog signal from one or more antennas.In some cases, the signal received by the peak detectors may have beenmodified, such as amplified, by one or more LNAs. In some cases, rootmean square (RMS) power voltage may also be used.

At block 408 a voltage level of the received RF signal is determined.For example, one or more of the peak detectors may measure a signalvoltage level of the received RF signal. At block 410 the voltage levelof the received RF signal is compared to the reliability threshold todetermine that a reliability condition exists. For example, if thevoltage level is equal or above a reliability threshold power level,then a relative reliability condition exists. In some cases, thiscomparison may be performed by a reliability detector, such areliability detector 210. At block 410, in response to the determinationthat the reliability condition exists, overriding the presentattenuation level set by the gain controller with an overrideattenuation level based on the present attenuation level. For example,the DSA attenuation setting may be overridden, by a gain controller suchas gain controller 222, with a predetermined value, where thepredetermined value is based on present DSA setting.

The term “couple” is used throughout the specification. The term maycover connections, communications, or signal paths that enable afunctional relationship consistent with the description of the presentdisclosure. For example, if device A generates a signal to controldevice B to perform an action, in a first example device A is coupled todevice B, or in a second example device A is coupled to device B throughintervening component C if intervening component C does notsubstantially alter the functional relationship between device A anddevice B such that device B is controlled by device A via the controlsignal generated by device A.

Modifications are possible in the described embodiments, and otherembodiments are possible, within the scope of the claims.

What is claimed is:
 1. A receiver comprising: an RF peak detector coupled to a reliability detector wherein the RF peak detector is configured to: receive a radio frequency (RF) signal; and determine a voltage level of the received RF signal; wherein the reliability detector module is configured to determine a relative reliability threshold based on a present attenuation level; an override value module coupled to the reliability detector module configured to: compare the voltage level of the received RF signal to the relative reliability threshold to determine that a reliability condition exists; and override, in response to the determination that the reliability condition exists, the present attenuation level set by the gain controller with an override attenuation level based on the present attenuation level; and a gain compensation value module coupled to the override value module wherein the gain compensation value module is configured to set the present attenuation level for an attenuator.
 2. The receiver of claim 1, wherein the override value module is further configured to update the relative reliability threshold based on the override attenuation level.
 3. The receiver of claim 1, wherein the attenuator is coupled to a RF analog to digital converter (RF-ADC) and wherein the receiver includes one or more gain compensation modules configured to apply a gain compensation to an output signal of the RF-ADC.
 4. The receiver of claim 3, wherein an amount of gain compensation is based on the override attenuation level and present attenuation level.
 5. The receiver of claim 4, wherein the override value module is further configured to: receive an updated attenuation level from the gain controller; and determine to release the override based on at least one of: a maximum time duration; an indication from a peak detector; or a comparison between the updated attenuation level, the override attenuation level, and a decay threshold.
 6. The receiver of claim 4, wherein the override value module is further configured to: receive an updated attenuation level from the gain controller; determine not to release the override based on a comparison between the updated attenuation level and a decay threshold; and update the gain compensation based on the updated attenuation level.
 7. The receiver of claim 3, wherein the receiver further comprises a gain compensation module coupled to a peak detector wherein the gain compensation module is configured to apply a gain compensation to an output from the peak detector.
 8. The receiver of claim 1, wherein the override value module is further configured to: determine to apply an absolute reliability threshold based on a comparison between an absolute reliability threshold and the relative reliability threshold for the present attenuation level; and wherein the reliability detector is configured to compare the voltage level of the received RF signal to the absolute reliability threshold to determine that an absolute reliability condition exists; and wherein the override value module is further configured to override, in response to the determination that the absolute reliability condition exists, based on an absolute reliability attenuation level.
 9. An electronic device comprising: one or more processors; a memory; an RF peak detector coupled to a reliability detector wherein the RF peak detector is configured to: receive a radio frequency (RF) signal; and determine a voltage level of the received RF signal; wherein the reliability detector module is configured to determine a relative reliability threshold based on a present attenuation level; an override value module coupled to the reliability detector module configured to: compare the voltage level of the received RF signal to the relative reliability threshold to determine that a reliability condition exists; and override, in response to the determination that the reliability condition exists, the present attenuation level set by the gain controller with an override attenuation level based on the present attenuation level; and a gain compensation value module coupled to the override value module configured to set the present attenuation level for an attenuator.
 10. The electronic device of claim 9, wherein the override value module is further configured to update the relative reliability threshold based on the override attenuation level.
 11. The electronic device of claim 9, wherein the attenuator is coupled to a RF analog to digital converter (RF-ADC) and wherein the receiver includes one or more gain compensation modules configured to apply a gain compensation to an output signal of the RF-ADC.
 12. The electronic device of claim 11, wherein an amount of gain compensation is based on the override attenuation level and present attenuation level.
 13. The electronic device of claim 11, wherein the override value module is further configured to: receive an updated attenuation level from the gain controller; and determine to release the override based on at least one of: a maximum time duration; an indication from a peak detector; or a comparison between the updated attenuation level, the override attenuation level, and a decay threshold.
 14. The electronic device of claim 12, wherein the override value module is further configured to: receive an updated attenuation level from the gain controller; determine not to release the override based on a comparison between the updated attenuation level and a decay threshold; and update the gain compensation based on the updated attenuation level.
 15. The electronic device of claim 11, wherein the receiver further comprises a gain compensation module coupled to a peak detector wherein the gain compensation module is configured to apply a gain compensation to an output from the peak detector.
 16. The receiver of claim 9, wherein the override value module is further configured to: determine to apply an absolute reliability threshold based on a comparison between an absolute reliability threshold and the relative reliability threshold for the present attenuation level; and wherein the reliability detector is configured to compare the voltage level of the received RF signal to the absolute reliability threshold to determine that an absolute reliability condition exists; and wherein the override value module is further configured to override, in response to the determination that the absolute reliability condition exists, based on an absolute reliability attenuation level. 